nuttx/arch/arm/src/sama5/sam_clockconfig.c

/****************************************************************************
 * arch/arm/src/sama5/sam_clockconfig.c
 *
 *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <debug.h>

#include <nuttx/arch.h>
#include <arch/board/board.h>

#include "up_arch.h"
#include "up_internal.h"

#include "sam_clockconfig.h"
#include "chip/sam_pmc.h"
#include "chip/sam_sfr.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Types
 ****************************************************************************/

/****************************************************************************
 * Public Data
 ****************************************************************************/

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: sam_pmcwait
 *
 * Description:
 *   Wait for the specide PMC status bit to become "1"
 *
 ****************************************************************************/

static void sam_pmcwait(uint32_t bit)
{
  /* There is no timeout on this wait.  Why not?  Because the symptoms there
   * is no fallback if the wait times out and if the wait does time out, it
   * can be very difficult to determine what happened.  Much better to just
   * hang here.
   */

  while ((getreg32(SAM_PMC_SR) & bit) == 0);
}

/****************************************************************************
 * Name: sam_enablemosc
 *
 * Description:
 *   Enable the main osciallator
 *
 ****************************************************************************/

static inline void sam_enablemosc(void)
{
  uint32_t regval;

  /* Switch from the internal 12MHz RC to the main external oscillator */

  if ((getreg32(SAM_PMC_CKGR_MOR) & PMC_CKGR_MOR_MOSCSEL) == 0)
    {
      /* Enable main external oscillator */

      regval  = getreg32(SAM_PMC_CKGR_MOR);
      regval |= PMC_CKGR_MOR_MOSCXTEN | PMC_CKGR_MOR_KEY;
      putreg32(regval, SAM_PMC_CKGR_MOR);

      /* Wait for the main clock to become ready  */

      while ((getreg32(SAM_PMC_CKGR_MCFR) & PMC_CKGR_MCFR_MAINFRDY) == 0);

      /* Disable external OSC 12 MHz bypass */

      regval  = getreg32(SAM_PMC_CKGR_MOR);
      regval &= ~PMC_CKGR_MOR_MOSCXTBY;
      regval |= PMC_CKGR_MOR_KEY;
      putreg32(regval, SAM_PMC_CKGR_MOR);

      /* Switch main clock source to the external oscillator */

      regval  = getreg32(SAM_PMC_CKGR_MOR);
      regval |= (PMC_CKGR_MOR_MOSCSEL | PMC_CKGR_MOR_KEY);
      putreg32(regval, SAM_PMC_CKGR_MOR);

      /* Wait for the main clock status change for the external oscillator
       * selection.
       */

      sam_pmcwait(PMC_INT_MOSCSELS);

      /* And handle the case where MCK is running on main CLK */

      sam_pmcwait(PMC_INT_MCKRDY);
    }
}

/****************************************************************************
 * Name: sam_selectmosc
 *
 * Description:
 *   Select the main oscillator as the input clock for processor clock (PCK)
 *   and the main clock (MCK).  The PCK and MCK differ only by the MDIV
 *   divisor that permits the MCK to run at a lower rate.
 *
 ****************************************************************************/

static inline void sam_selectmosc(void)
{
  uint32_t regval;

  /* Select the main oscillator as the input clock for PCK and MCK */

  regval  = getreg32(SAM_PMC_MCKR);
  regval &= ~PMC_MCKR_CSS_MASK;
  regval |= PMC_MCKR_CSS_MAIN;
  putreg32(regval, SAM_PMC_MCKR);

  /* Wait for main clock to be ready */

  sam_pmcwait(PMC_INT_MCKRDY);
}

/****************************************************************************
 * Name: sam_pllasetup
 *
 * Description:
 *   Select the main oscillator as the input clock for processor clock (PCK)
 *   and the main clock (MCK).  The PCK and MCK differ only by the MDIV
 *   divisor that permits the MCK to run at a lower rate.
 *
 ****************************************************************************/

static inline void sam_pllasetup(void)
{
  uint32_t regval;

  /* Configure PLLA */

  regval = (BOARD_CKGR_PLLAR_DIV | BOARD_CKGR_PLLAR_COUNT |
            BOARD_CKGR_PLLAR_OUT | BOARD_CKGR_PLLAR_MUL |
            PMC_CKGR_PLLAR_ONE);
  putreg32(regval, SAM_PMC_CKGR_PLLAR);

  /* Set the PLL Charge Pump Current Register to zero */

  putreg32(0, SAM_PMC_PLLICPR);

  /* And wait for the PLL to lock on */

  sam_pmcwait(PMC_INT_LOCKA);
}

/****************************************************************************
 * Name: sam_plladivider
 *
 * Description:
 *   Configure MCK PLLA divider
 *
 ****************************************************************************/

static inline void sam_plladivider(void)
{
  uint32_t regval;

  /* Is the PLLA divider currently set? */

  regval = getreg32(SAM_PMC_MCKR);
  if ((regval & PMC_MCKR_PLLADIV2) != 0)
    {
#if BOARD_PMC_MCKR_PLLADIV == 0
      /* The divider is set and we are configured to clear it */

      regval &= ~PMC_MCKR_PLLADIV2;
#else
      /* The divider is already set */

      return;
#endif
    }
  else
    {
#if BOARD_PMC_MCKR_PLLADIV == 0
      /* The divider is already cleared */

      return;
#else
      /* The divider is clear and we are configured to set it */

      regval |= PMC_MCKR_PLLADIV2;
#endif
    }

  /* We changed the PLLA divider.  Wait for the main clock to be ready again */

  sam_pmcwait(PMC_INT_MCKRDY);
}

/****************************************************************************
 * Name: sam_mckprescaler
 *
 * Description:
 *   Configure main clock (MCK) Prescaler
 *
 ****************************************************************************/

static inline void sam_mckprescaler(void)
{
  uint32_t regval;

  /* Set the main clock prescaler */

  regval  = getreg32(SAM_PMC_MCKR);
  regval &= ~PMC_MCKR_PRES_MASK;
  regval |= BOARD_PMC_MCKR_PRES;
  putreg32(regval, SAM_PMC_MCKR);

  /* Wait for the main clock to be ready again */

  sam_pmcwait(PMC_INT_MCKRDY);
}

/****************************************************************************
 * Name: sam_mckdivider
 *
 * Description:
 *   Configure main clock (MCK) divider (MDIV).  This divider allows the MCK
 *   to run at a lower rate then PCK.
 *
 ****************************************************************************/

static inline void sam_mckdivider(void)
{
  uint32_t regval;

  /* Set the main clock divider */

  regval  = getreg32(SAM_PMC_MCKR);
  regval &= ~PMC_MCKR_MDIV_MASK;
  regval |= BOARD_PMC_MCKR_MDIV;
  putreg32(regval, SAM_PMC_MCKR);

  /* Wait for the main clock to be ready again */

  sam_pmcwait(PMC_INT_MCKRDY);
}

/****************************************************************************
 * Name: sam_selectplla
 *
 * Description:
 *   Select the PLLA output as the input clock for PCK and MCK.
 *
 ****************************************************************************/

static inline void sam_selectplla(void)
{
  uint32_t regval;

  /* Select the PLLA output as the main clock input */

  regval  = getreg32(SAM_PMC_MCKR);
  regval &= ~PMC_MCKR_CSS_MASK;
  regval |= PMC_MCKR_CSS_PLLA;
  putreg32(regval, SAM_PMC_MCKR);

  /* Wait for the main clock to be ready again */

  sam_pmcwait(PMC_INT_MCKRDY);
}

/****************************************************************************
 * Name: sam_upllsetup
 *
 * Description:
 *   Select the PLLA output as the input clock for PCK and MCK.
 *
 ****************************************************************************/

static inline void sam_upllsetup(void)
{
#ifdef CONFIG_USBDEV
  uint32_t regval;

  /* Setup UTMI for USB and wait for LOCKU */

  regval = getreg32(SAM_PMC_CKGR_UCKR);
  regval |= (BOARD_CKGR_UCKR_UPLLCOUNT | PMC_CKGR_UCKR_UPLLEN);
  putreg32(regval, SAM_PMC_CKGR_UCKR);

  sam_pmcwait(PMC_INT_LOCKU);
#endif
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: sam_clockconfig
 *
 * Description:
 *   Called to initialize the SAM3/4.  This does whatever setup is needed to
 *   put the SoC in a usable state.  This includes the initialization of
 *   clocking using the settings in board.h.  (After power-on reset, the SAM3/4
 *   is initially running on a 12MHz internal RC clock).  This function also
 *   performs other low-level chip initialization of the chip including master
 *   clock, IRQ & watchdog configuration.
 *
 * Boot Sequence
 *
 *   This logic may be executing in ISRAM or in external mmemory: CS0, DDR,
 *   CS1, CS2, or CS3.  It may be executing in CS0 or ISRAM through the
 *   action of the SAMA5 "first level bootloader;"  it might be executing in
 *   CS1-3 through the action of some second level bootloader that provides
 *   configuration for those memories.
 *
 *   The system always boots from the ROM memory at address 0x0000:0000,
 *   starting the internal first level bootloader.  That bootloader can be
 *   configured to work in different ways using the BMS pin and the contents
 *   of the Boot Sequence Configuration Register (BSC_CR).
 *
 *   If the BMS_BIT is read "1", then the first level bootloader will
 *   support execution of code in the memory connected to CS0 on the EBI
 *   interface (presumably NOR flash).  The following sequence is performed
 *   by the first level bootloader if BMS_BIT is "1":
 *
 *     - The main clock is the on-chip 12 MHz RC oscillator,
 *     - The Static Memory Controller is configured with timing allowing
 *       code execution in CS0 external memory at 12 MHz
 *     - AXI matrix is configured to remap EBI CS0 address at 0x0
 *     - 0x0000:0000 is loaded in the Program Counter register
 *
 *   The user software in the external memory must perform the next
 *   operation in order to complete the clocks and SMC timings configuration
 *   to run at a higher clock frequency:
 *
 *     - Enable the 32768 Hz oscillator if best accuracy is needed
 *     - Reprogram the SMC setup, cycle, hold, mode timing registers for EBI
 *       CS0, to adapt them to the new clock.
 *     - Program the PMC (Main Oscillator Enable or Bypass mode)
 *     - Program and Start the PLL
 *     - Switch the system clock to the new value
 *
 *  If the BMS_BIT is read "0", then the first level bootloader will
 *  perform:
 *
 *     - Basic chip initialization: XTal or external clock frequency
 *       detection:
 *
 *       a. Stack Setup for ARM supervisor mode
 *       b. Main Oscillator Detection:  The bootloader attempts to use an
 *          external crystal.  If this is not successful, then  the 12 MHz
 *          Fast RC internal oscillator is used as the main osciallator.
 *       c. Main Clock Selection: The Master Clock source is switched from
 *          to the main oscillator without prescaler. PCK and MCK are now
 *          the Main Clock.
 *       d. PLLA Initialization: PLLA is configured to get a PCK at 96 MHz
 *          and an MCK at 48 MHz. If an external clock or crystal frequency
 *          running at 12 MHz is found, then the PLLA is configured to allow
 *          USB communication.
 *
 *     - Attempt to retrieve a valid code from external non-volatile
 *       memories (NVM): SPI0 CS0 Flash Boot, SD Card Boot, NAND Flash Boot,
 *       SPI0 CS1 Flash Boot, or TWI EEPROM Boot.  Different heuristics are
 *       used with each media type.  If a valid image is found, it is copied
 *       to internal SRAM and started.
 *
 *     - In case no valid application has been found on any NVM, the SAM-BA
 *       Monitor is started.
 *
 ****************************************************************************/

void sam_clockconfig(void)
{
#ifdef CONFIG_SAMA5_BOOT_CS0FLASH
  bool config = false;
#endif

  /* Initialize clocking.
   *
   * Check first:  Are we running in CS0?
   */

#ifdef CONFIG_SAMA5_BOOT_CS0FLASH
  /* Yes... did we get here via the first level bootloader? */

  if ((getreg32(SAM_SFR_EBICFG) & SFR_EBICFG_BMS) != 0)
    {
      /* Yes.. Perform the following operations in order to complete the
       * clocks and SMC timings configuration to run at a higher clock
       * frequency:
       *
       *   - Enable the 32768 Hz oscillator if best accuracy is needed
       *   - Reprogram the SMC setup, cycle, hold, mode timing registers for EBI
       *     CS0, to adapt them to the new clock.
       *   - Program the PMC (Main Oscillator Enable or Bypass mode)
       *   - Program and Start the PLL
       *   - Switch the system clock to the new value
       */
#error Missing logic

      config = true;
    }
#endif

  /* If we are running from DDRAM or CS1-3, then we will not modify the
   * clock configuration.  In these cases, we have to assume that some
   * secondary bootloader started us here and that the bootloader has
   * configured clocking appropriately.
   *
   * If we are running in CS0, then we may have been started by either
   * the first or second level bootloader.  In either case, we need to
   * update the PLLA settings in order to get a higher performance
   * clock.
   */

#ifdef CONFIG_SAMA5_BOOT_CS0FLASH
  if (config)
#endif /* CONFIG_SAMA5_BOOT_CS0FLASH */
#if defined(CONFIG_SAMA5_BOOT_ISRAM) || defined(CONFIG_SAMA5_BOOT_CS0FLASH)
    {
      /* Enable main oscillator (if it has not already been selected) */

      sam_enablemosc();

      /* Select the main oscillator as the input clock for processor clock
       * (PCK) and the main clock (MCK).  The PCK and MCK differ only by the
       * MDIV divisor that permits the MCK to run at a lower rate.
       */

      sam_selectmosc();

      /* Setup PLLA */

      sam_pllasetup();

      /* Configure the MCK PLLA divider. */

      sam_plladivider();

      /* Configure the MCK Prescaler */

      sam_mckprescaler();

      /* Configure MCK Divider */

      sam_mckdivider();

      /* Finally, elect the PLLA output as the input clock for PCK and MCK. */

      sam_selectplla();

      /* Setup UTMI for USB */

      sam_upllsetup();
    }
#endif /* CONFIG_SAMA5_BOOT_ISRAM || CONFIG_SAMA5_BOOT_CS0FLASH */
}